Django-filter: Contiene / filtro icontains no funciona

class OrderFilter(django_filters.FilterSet):
    class Meta:
        model = Order
        fields = {
            'status': ['exact',],
            'client': ['icontains',],
        }

class OrderViewset(viewsets.ModelViewSet):
    filter_class = OrderFilter
    permission_classes = ( permissions.IsAuthenticated, )
    serializer_class = OrderSerializer
    queryset = Order.objects.all()
    filter_backends = (
        filters.OrderingFilter,
        filters.SearchFilter,
        filters.DjangoFilterBackend
    )
    ordering_fields = ('added_at', 'status', 'client', 'order_number')
    ordering = ('-added_at',)

class Order(models.Model):
    order_number = models.CharField(max_length=255, default='')
    client = models.CharField(max_length=255, default='')
    status = models.CharField(max_length=255, default='')
    added_at = models.DateTimeField(auto_now_add=True)

Básicamente, se ignora el filtro de cliente. Si reemplazo icontains con exact, funciona.
Pero no puedo hacer que los contenidos o icontains funcionen en ningún campo.

Requirements.txt:

Django == 1.10.4
psycopg2 == 2.6.2
djangorestframework == 3.5.3
canales == 1.0.0
djangorestframework-jwt == 1.9.0
filtro django == 1.0.1
asgi-redis == 1.0.0
daphne == 1.0.0